TOYOTA COROLLA ENGINE PROBLEM

2005 Toyota Corolla • 110,000 miles

My corolla D4D cuts out and throws up the fault code P0093 which is a fuel leak fault. The strange thing is that it only happens in cold weather, and only then before the engine is up to running temperature. It never happens in the summer time or when the engine is warm. Our local diesel specialists thought it was the pump pressure regulator which I have changed, but its no better.
Any ideas?